Such a flat-shaped administration form is a dermal or transdermal therapeutic system in the form of a patch, for example, described in DE 36 29 304. There an active substance depot with textile sheet material is surrounded by a matrix on all sides; metering the active substance into the depot is particularly difficult. DE 36 30 603 and EP 0 219 762 propose to apply the active substance-containing mass by means of a roll coater. A similar proposal is made in DE 38 44 250 where the active substance is printed in flowable form on a web-shaped absorbent textile substrate. Engraved roll coating, extrusion coating, screen printing, or spray coating are mentioned as possible printing methods.
However, these methods have some shortcomings. On the one hand, the active substance is applied on the whole continuous web, although only defined sections of the web-shaped material can normally be used for the actual administration form; this results in large quantities of active substance-containing waste.
On the other hand, the skilled artisan knows that the accuracy specified for therapeutic systems can only hardly, if at all, be achieved. This also applies to the processes proposed in DE 35 31 795, such as screen printing, flexoprinting, gravure printing, and inkjetting.
A practical method avoiding active substance-containing waste is the tampon printing method described in DE 37 27 214 and DE 37 27 232. The disadvantage in this case lies in the fact that the amount of liquid filled in the printing block as well as that transferred by the tampon depends on factors that are difficult to control, such as temperature, viscosity, printing rate, pressure on the support, and surface property. For this reason the demands with respect to accuracy are also difficult to meet. Controlling the transferred amount is only possible outside the actual manufacturing process by printing preweighed patterns.
An improvement can be achieved by the process described in P 42 30 589.6; here the tampon presses the web material directly into the filled cavity of a printing block where it absorbs the liquid active substance. Again, the disadvantage is that the printing block cannot be filled exactly, and that the liquid active substance preparation must have a medium to high viscosity .
An absolutely different way is described in DE 34 23 328. Here adhesive and active substance are physically separated and printed in the form of dots by means of screen printers. However, the disadvantages of this method are that the printed area only forms a very small part of the total surface, on the one hand, and that the above-mentioned restrictive conditions with respect to accuracy are applicable in this case too.